Monday, February 18, 2013

a few more hooked knives

I really like these things.  I figure if I make enough of them, I'll  make enough mistakes to start learning things.
I annealed some more spring steel, then used a sawzall to halve it.  So fast!
 grinding down to the pits

 using nail polish as bluing to find the high spots.  I put some nail polish on the table, then rub the part in it.  The highest spots have rings of color around them.  I do some more fine grinding before switching to sandpaper.
 sketching out the profiles
 after rough grinding and some filing.  The annealed spring steel files nicely.  However, the bench grinder is much faster.

 further sharpening on a stone
 trying out the strop with some fine honing compound
 I then made the two profiles.  We'll see how they perform.

 In an experiment in impracticality, I made the brass 8-32 screws and square nuts on the lathe.  It took a while.  Brass is friendly though.

The two knives seem to work well.  I think the heat treating process was a success.  They hold an edge pretty well, and the long knife is just slightly springy.  I can get it to sound by plucking it.

An addendum:  I recently broke one of these knives (late 2013)  It snapped where the blade meets the tang.  This is likely due to a failure in my heat treating.  If I had to guess, I'd say the steel was 5160, as it came from some well aged leaf springs.  (~1960s jeep)  I quenched from an orange heat in water.  They were tempered in an electric furnace.  The furnace was not calibrated, so I did it by monitoring the oxidation colors on a number of fresh steel samples put into the furnace and slowly incrementing the temperature.

In future, I plan to oil quench (the internet consensus for 5160 knives).


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